Weird MegaST issue..

[Bikerbob]

I was doing the A/B mod to this computer, it was screwing up.. and I could not figure it out. I have removed the mod.. completely. I still have the problem.. So its not my mod..

The computer will access an internal drive np..

If I plug a external drive in ( I Have tried 2 drives, two controllers , two cables) when I try and access drive B - external - it will access both A &B - SO my internal drive on this computer is getting both D0SEL and D1SEL - it is trying to read and the head moves just as if I was using drive A - but trying on drive B - Sometimes it will work, other times no.. but this is not supposed to be happening. I have looked over the schematic, the board, and I cannot figure out how this can be happening.

Open to suggestions.

James

[frank.lukas]

Atari floppy disks are always jumped as a drive A (DS0), regardless of whether they are internal or external. So check what have you modify?

[Bikerbob]

Atari floppy disks are always jumped as a drive A (DS0), regardless of whether they are internal or external. So check what have you modify?

Frank, these same drives all work perfectly fine on other machines. I have 8 different ST machines here at the moment. They are Std DD external drives and the internal drives are all SMD-380 (DD) and SMD-340(HD) drives. All jumpered correctly to work in any machine.

This is why this was so frustrating and baffling. I though I had done something wrong with the A/B mod.. in fact there is a problem on the MB causing this. I will try a few different cables.. maybe there is something to that???

James

[frank.lukas]

What have you done/mod on the shugart internal bus ?

[Bikerbob]

Seems like it was a cable.. and I even had 2 of them.. bought them a while back.. seemed like great cables..

cable.jpg

no idea why.. but they look fine, in the package.. new.. but they caused all this. 34pin std ribbon cables work perfect.

James

[rubber_jonnie]

Do the cables have a twist in them? Those are not suitable for the ST.